The invention relates to a film guide for a movie camera.
In order to provide a film guide for movie films in movie cameras, an image window section of an image window is arranged in the optical beam path of the recording objective of the movie camera. The image window section defines the size of the area of the individual images of the movie film to be exposed. Herein, the film plane of the image window section is opposite the film plane of a gripper platform and of a spacing window being integrated in the gripper platform in such a way that, between the two film planes, a film channel is formed between the image window and the gripper platform. In this way, a film gap is formed between the image window and the spacing window to guide the movie film. The film channel and film gap hold the movie film in one image plane, thus ensuring a constant level of contact with respect to the camera objective and thus a constant focusing plane for the movie film during the exposure of the individual images.
The film channel or film gap which is formed between the image window on the one hand and the gripper platform and the spacing window on the other hand is of such a size that, on the one hand, the focusing plane remains constant in the area of the image window section during exposure of the individual images of the movie film and, on the other hand, neither fluttering of the movie film nor increased friction between the movie film and the frame of the image window as well as of the film plane surface of the gripper platform and of the spacing window occurs, which would lead to noise, to damage to the movie film and to increased film transport resistance. In order to minimize the friction on the movie films during film transport through the film channel and film gap, the gripper platform has side sliding webs on which the normally perforated edge of the movie film slides, and the spacing window has so-called sliding webs which, for example, extend in the movement direction of the movie film and rest against the rear face of the movie film, so that the entire surface of the movie film does not make contact with the spacing window.
DE 85 31 946 U1 discloses a movie film recording camera having guide surfaces which form a film guide channel, via which the film is passed, such that it slides, in feed and take-up areas to and from an image window and in the area of the image window, to be precise between the image window and a film contact-pressure plate. In order to ensure minimal and uniform friction in the film guide channel, and thus easy sliding as well as a minimal load on and damage to the film during film transport, even in the event of major temperature fluctuations, the guide surfaces have a corrugated surface, with the corrugation peaks and corrugation troughs being arranged transversely with respect to the film running direction.
For intermittent film transport, a film transport mechanism is provided in a movie camera and has a gripper switching mechanism which is arranged in a drive module and has one or more gripper tips on a single-sided or double-sided gripper, which engage through elongated opening slots in the gripper platform in the film perforations which are arranged at the side of the film images to be exposed, and transports the movie film onwards by one film image in each case for each film transport step. When the film image is in the stationary phase, at least one blocking gripper engages through a hole in the gripper platform in the film perforation in the movie film, and ensures that the image is stationary while the film is being exposed.
In order to make it easier to insert the movie film into a movie camera, the drive module can be moved or pivoted with respect to the image window together with the spacing window which is supported on the gripper platform of the drive module, so that the film channel between the image window and the gripper platform and the film gap between the image window and the spacing window are enlarged in order to hold the movie film. The spacing window is connected to the gripper platform via adjusting screws, which support the spacing window on the gripper platform, with the spacing window being sprung with respect to the gripper platform via one or more contact-pressure levers. This results in the size and parallelity of the film gap being ensured via a plurality of moving parts, specifically via the adjusting screws, the springing and the gripper platform which moves with the drive module.
After movement or pivoting of the drive module for insertion of a movie film, this can lead, for example, to the size of the film channel and/or film gap being increased or decreased and to loss of parallelity between the opposite image planes of the image window and of the spacing window, so that the focusing plane is not ensured in all areas of the film channel and film gap, and/or excessive friction of the movie film occurs.